Characterization of phiCFP-1, a virulent bacteriophage specific for Citrobacter freundii

Citrobacter freundii, a Gram‐negative bacterium, causes many opportunistic infections. Bacteriophage phiCFP‐1 was isolated and characterized by its ability to lyse the multidrug‐resistant clinical C. freundii strain P10159. Transmission electron microscopy showed that the phage has an icosahedral head and a short tail, making it a Podoviridae family member. In a single‐step growth experiment, phiCFP‐1 exhibited an eclipse period of 20 min and a burst size of 100 particles per cell. Its genome assembled as a circular molecule when genomic sequencing was completed. However, based on genome content and organization, it was categorized as a classic T7‐related phage, and such phages are known to have linear genomes with direct terminal repeats. With the quick and simple method established herein, the 38,625‐bp linear double‐stranded DNA with 229‐bp direct terminal repeats was accurately identified. The genome contained 43 putative open reading frames and no tRNA genes. Using a proteomics‐based approach, seven viral and two host proteins from purified phiCFP‐1 particles were identified. Comparative genomics and recombination analyzes revealed close genetic relatedness among phiCFP‐1, phiYeO3‐12/vB_YenP_AP5 (from Yersinia enterocolitica O3), and phiSG‐JL2 (from Salmonella enterica). J. Med. Virol. 88:895–905, 2016. © 2015 Wiley Periodicals, Inc.